drm/i915: Remove lrc default desc from GEM context

We only compute the lrc_descriptor() on pinning the context, i.e.
infrequently, so we do not benefit from storing the template as the
addressing mode is also fixed for the lifetime of the intel_context.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Prathap Kumar Valsan <prathap.kumar.valsan@intel.com>
Acked-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190730133035.1977-9-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gem/i915_gem_context.c

@@ -397,30 +397,6 @@ static void context_close(struct i915_gem_context *ctx)
 	i915_gem_context_put(ctx);
 }
 
-static u32 default_desc_template(const struct drm_i915_private *i915,
-				 const struct i915_address_space *vm)
-{
-	u32 address_mode;
-	u32 desc;
-
-	desc = GEN8_CTX_VALID | GEN8_CTX_PRIVILEGE;
-
-	address_mode = INTEL_LEGACY_32B_CONTEXT;
-	if (vm && i915_vm_is_4lvl(vm))
-		address_mode = INTEL_LEGACY_64B_CONTEXT;
-	desc |= address_mode << GEN8_CTX_ADDRESSING_MODE_SHIFT;
-
-	if (IS_GEN(i915, 8))
-		desc |= GEN8_CTX_L3LLC_COHERENT;
-
-	/* TODO: WaDisableLiteRestore when we start using semaphore
-	 * signalling between Command Streamers
-	 * ring->ctx_desc_template |= GEN8_CTX_FORCE_RESTORE;
-	 */
-
-	return desc;
-}
-
 static struct i915_gem_context *
 __create_context(struct drm_i915_private *i915)
 {
@@ -459,7 +435,6 @@ __create_context(struct drm_i915_private *i915)
 	i915_gem_context_set_recoverable(ctx);
 
 	ctx->ring_size = 4 * PAGE_SIZE;
-	ctx->desc_template = default_desc_template(i915, NULL);
 
 	for (i = 0; i < ARRAY_SIZE(ctx->hang_timestamp); i++)
 		ctx->hang_timestamp[i] = jiffies - CONTEXT_FAST_HANG_JIFFIES;
@@ -478,8 +453,9 @@ __set_ppgtt(struct i915_gem_context *ctx, struct i915_address_space *vm)
 	struct i915_gem_engines_iter it;
 	struct intel_context *ce;
 
+	GEM_BUG_ON(old && i915_vm_is_4lvl(vm) != i915_vm_is_4lvl(old));
+
 	ctx->vm = i915_vm_get(vm);
-	ctx->desc_template = default_desc_template(ctx->i915, vm);
 
 	for_each_gem_engine(ce, i915_gem_context_lock_engines(ctx), it) {
 		i915_vm_put(ce->vm);

drivers/gpu/drm/i915/gem/i915_gem_context_types.h

@@ -171,8 +171,6 @@ struct i915_gem_context {
 
 	/** ring_size: size for allocating the per-engine ring buffer */
 	u32 ring_size;
-	/** desc_template: invariant fields for the HW context descriptor */
-	u32 desc_template;
 
 	/** guilty_count: How many times this context has caused a GPU hang. */
 	atomic_t guilty_count;

drivers/gpu/drm/i915/gt/intel_lrc.c

@@ -417,13 +417,17 @@ lrc_descriptor(struct intel_context *ce, struct intel_engine_cs *engine)
 	BUILD_BUG_ON(MAX_CONTEXT_HW_ID > (BIT(GEN8_CTX_ID_WIDTH)));
 	BUILD_BUG_ON(GEN11_MAX_CONTEXT_HW_ID > (BIT(GEN11_SW_CTX_ID_WIDTH)));
 
-	desc = ctx->desc_template;				/* bits  0-11 */
-	GEM_BUG_ON(desc & GENMASK_ULL(63, 12));
+	desc = INTEL_LEGACY_32B_CONTEXT;
+	if (i915_vm_is_4lvl(ce->vm))
+		desc = INTEL_LEGACY_64B_CONTEXT;
+	desc <<= GEN8_CTX_ADDRESSING_MODE_SHIFT;
+
+	desc |= GEN8_CTX_VALID | GEN8_CTX_PRIVILEGE;
+	if (IS_GEN(engine->i915, 8))
+		desc |= GEN8_CTX_L3LLC_COHERENT;
 
 	desc |= i915_ggtt_offset(ce->state) + LRC_HEADER_PAGES * PAGE_SIZE;
 								/* bits 12-31 */
-	GEM_BUG_ON(desc & GENMASK_ULL(63, 32));
-
 	/*
 	 * The following 32bits are copied into the OA reports (dword 2).
 	 * Consider updating oa_get_render_ctx_id in i915_perf.c when changing

drivers/gpu/drm/i915/gvt/scheduler.c

@@ -291,9 +291,6 @@ shadow_context_descriptor_update(struct intel_context *ce,
 	 * Update bits 0-11 of the context descriptor which includes flags
 	 * like GEN8_CTX_* cached in desc_template
 	 */
-	desc &= U64_MAX << 12;
-	desc |= ce->gem_context->desc_template & ((1ULL << 12) - 1);
-
 	desc &= ~(0x3 << GEN8_CTX_ADDRESSING_MODE_SHIFT);
 	desc |= workload->ctx_desc.addressing_mode <<
 		GEN8_CTX_ADDRESSING_MODE_SHIFT;